1980—2020年大湾区海岸线变迁及影响因素分析

海岸线动态变化是全球变化和人类活动共同的反映。本文基于粤港澳大湾区、东京湾和旧金山湾1980—2020年7期Landsat系列遥感影像及Google Earth高分辨率影像, 利用阈值分割, 结合水体指数法、Sobel算子法, 提取各期海岸线。从长度、空间形态、结构和利用程度等多角度分析其岸线变化, 并结合地理探测器对其影响因素进行定性和定量分析。结果显示: 1) 1980—2020年间, 各湾区岸线趋于平直, 其中东京湾海岸线的年均长度变化强度最大, 为0.37%; 2) 40a间各湾区岸线的纵深变化比较稳定, 结构趋于复杂, 形态趋于分散, 其中粤港澳大湾区海岸线的分维差异最小, 形态最分散; 3) 40a间, 各湾区的自然岸线减少, 港口码头岸线和其他人工岸线长度剧烈增长, 其中粤港澳大湾区的生物岸线波动增长, 岸线利用程度指数增幅最大。本文研究结果表明, 气温、波高、潮汐和陆域面积、港口吞吐量是湾区海岸线变化的主要影响因素, 且任意两个影响因素的交互作用大于单一因素的作用。

Analyzing the coastline changes and its influencing factors in the Greater Bay Area from 1980 to 2020

Coastline dynamic change is a common reflection of global change and human activities. Based on seven Landsat remote sensing images and Google Earth high-resolution images of the Guangdong-Hong Kong-Macao Greater Bay Area, Tokyo Bay and San Francisco Bay from 1980 to 2020, this paper used threshold segmentation combined with water index method and Sobel operator method to extract the coastline of each analysis period. In addition, this study also analyzed the changes of coastline in terms of length, spatial morphology, structure and utilization degree, and analyzed qualitatively and quantitatively the influencing factors with the help of geographic detectors. The results show that: (1) from 1980 to 2020, the intensity of annual average length change in the Tokyo Bay is the largest, which is 0.37%, and the coastline tends to be straight; (2) in the past 40 years, the depth of coastlines in all analyzed bay areas has remained stable, and the structures tend to be complex and the morphology tends to be dispersed. Among them, the difference of fractal dimension of coastlines in the Guangdong-Hong Kong-Macao Greater Bay Area is the smallest and the morphology is the most dispersed; (3) during the past 40 years, the natural coastline of each bay area decreased, while the length of port wharf coastline and other artificial coastline increased significantly, and the biological coastline of the Guangdong-Hong Kong-Macao Greater Bay Area fluctuated, and the coastline utilization index increased the most. The results show that temperature, wave height, tide, area and port throughput are the main factors that affect the coastline change, the interaction of any two factors is greater than the single factor.